1. Technical Field
The present disclosure generally relates to printed circuit boards (PCBs), and particularly, relates to a method for manufacturing a printed circuit board with a cavity.
2. Description of Related Art
To accommodate development of miniaturized electronic products with multiple functions, multilayer printed circuit boards are widely used due to their special characteristics such as micromation, lightness, and high-density interconnectiblity.
Many electronic elements need to be packaged on the PCB, in electronic communication with the electrically conductive traces of the PCB. In order to reduce packaging height, a cavity for receiving the electronic elements is formed when manufacturing the PCB. Some of the electrically conductive traces in an inner layer in the cavity are exposed. A method for manufacturing the PCB with cavity generally includes a step of laminating an adhesive sheet and an outer electrically conductive layer on an inner layer substrate having electrically conductive traces. The adhesive sheet is generally pre-preg. The pre-preg includes B-stage resin. When the pre-preg is heated and pressed, the resin in the pre-preg can flow and have an adhesive ability, thus the inner layer substrate and the outer electrically conductive layer are adhered by the adhesive sheet. When the adhesive sheet is hot pressed, the overflow of resin in the adhesive sheet is hard to control. The overflow of resin on the electrically conductive traces is hard to remove, such that the PCB with a cavity has to be discarded.
What is needed, therefore, is a method for manufacturing a printed circuit board with cavity to overcome the above-described problems.